1. Field of the Invention
The present invention relates to improvement in a semiconductor device including a layer of nitride-based compound semiconductor (InxAlyGa1-x-yN: 0≦x, 0≦y, x+y<1), and improvement in a producing method thereof.
2. Description of the Background Art
Japanese Patent Laying-Open No. 06-196757 discloses a method of producing a nitride-based semiconductor device, which can be used for producing a blue light-emitting diode, a blue laser diode or the like. According to the disclosure of Japanese Patent Laying-Open No. 06-196757, a GaN buffer layer is grown to about 20 nm thickness on a sapphire substrate at a substrate temperature of 510° C. On the GaN buffer layer, a GaN layer is grown to about 2 μm thickness at a substrate temperature of 1030° C. Further, on the GaN layer, an InGaN light-emitting layer is grown at a substrate temperature of 800° C.
When the GaN buffer layer is grown at the low temperature of 510° C. as disclosed in Japanese Patent Laying-Open No. 06-196757, the grown GaN buffer layer is in an amorphous state. When the GaN layer is grown at the high temperature of 1030° C. on the amorphous GaN buffer layer, dislocations are generated from the interface with the amorphous GaN buffer layer and then extend penetrating or threading through the GaN layer being grown at the high temperature. When the InGaN light-emitting layer is grown at the high temperature of 800° C. on the GaN layer including such threading dislocations, the threading dislocations propagate into the light-emitting layer. As a result, in a nitride-based semiconductor light-emitting device produced with the light-emitting layer including such threading dislocations, its light-emitting efficiency becomes low due to the threading dislocations.